Method and device for contactless oscillation measurement

Abstract

The invention relates to a method and to a device for the contactless oscillation measurement of an object, comprising: a rotating device that can be rotated about an axis of rotation for positioning the object; a laser interferometer, the direction of the measuring beam of which can be changed by means of the beam guiding unit; and an evaluation unit for determining the measurement points, assigning the oscillation data from the laser interferometer to the measurement points and evaluating the measurement points, which cooperates with the control unit in order to direct the measurement light beam in succession to a plurality of predetermined measurement points on the object by means of the beam guiding unit. The control unit is further designed to rotate the rotary device at least once about the axis of rotation by a predetermined angle of rotation [phi] in a motorized manner or to sense such rotation by angle measurement, after which the at least one measurement beam is directed sequentially towards a plurality of predetermined measurement points of the object. The output unit finally outputs the evaluated oscillation data, preferably in the object-dependent coordinate system, in association with the measurement point. Prior to the measurement, a spatial reference is established between the laser interferometer, the axis of rotation and the object.

Description

Technical Field

[0001] The present invention relates to a non-contact method for measuring object oscillations having the features of the preamble of claim 1, and an apparatus for non-contact oscillation measurement as described in the preamble of claim 17. Background Technology

[0002] Therefore, the method according to the invention relates to a method in which an object is first positioned on a support, and multiple measurement points are determined on the object. At least one laser interferometer is used, wherein such a laser interferometer may include one or more measurement heads to direct either a single measurement beam or multiple, preferably three, measurement beams from different spatial directions onto the measurement points simultaneously. For each measurement head, the direction of one or more measurement beams of the laser interferometer can be changed by means of a respective beam guiding unit to perform a scanning process without changing the position of the laser interferometer. "Position" within the scope of this invention refers to spatial positioning and orientation.

[0003] By sequentially pointing one or more measurement beams to a measurement point using one or more beam guiding units, oscillation data at the measurement point can be acquired (recorded, sensed). More precisely, this is achieved by superimposing the measurement beam reflected or scattered back from the object with a reference beam of a laser interferometer. If multiple measurement heads are present, each measurement beam is superimposed with its own reference beam. The oscillation data is then evaluated and assigned to the measurement point, and the evaluated oscillation data is output in association with the measurement point, preferably in an object-related coordinate system. This allows multiple measurement points and the oscillation data assigned to each measurement point to be displayed on the object using a CAD model or digital image.

[0004] According to the preamble of claim 17, the apparatus according to the invention relates to a device particularly suitable for performing the method according to the invention, and includes a support for positioning an object, and at least one laser interferometer including one or more measuring heads, the measuring beam of which can be oriented by means of a corresponding beam guiding unit, and thereby can also be displaced and / or have its spatial orientation changed relative to the object. In the laser interferometer, for each measuring head, oscillation data in a spatial direction corresponding to the corresponding laser beam direction can be acquired by superimposing the measuring beam reflected or scattered from a measuring point on the object with a reference beam. An evaluation unit determines the measuring points, assigns the oscillation data from the laser interferometer to the measuring points, and evaluates the oscillation data. The evaluation unit cooperates with a control unit that sequentially points one or more measuring beams onto the determined measuring points on the object by means of one or more beam guiding units. An output unit finally outputs the evaluated oscillation data associated with the measuring points, and more specifically preferably in an object-related coordinate system.

[0005] These methods and devices have long replaced traditional methods for measuring object oscillations, particularly vibrations, in which accelerometers are installed at specific measurement points on the surface of the object being measured. This is because accelerometers typically alter the oscillation characteristics of the object's surface; furthermore, installing and removing accelerometers is time-consuming and laborious.

[0006] An optical method for acquiring the oscillations of an object naturally avoids these drawbacks. To this end, a laser interferometer, typically a laser Doppler vibrometer, is used to illuminate each measurement point on the object with a coherent laser. The oscillating motion of the object's surface causes a Doppler frequency shift in the light reflected or scattered back from the surface. Analysis of the frequency shift provides the necessary oscillation data, as the corresponding velocity value along the direction of the measurement beam at the measurement point can be calculated from the frequency shift, and the acceleration value at the measurement point can also be calculated from its change. An example of this optical method is described in EP 1 431 740 A1.

[0007] A method and apparatus of the type described at the beginning having the features of the preamble of claims 1 and 17 is also known from DE 10 2007 023 826 A1.

[0008] EP 1 431 740 A1 proposes moving a laser interferometer to different measurement positions to enable measurement of an object from multiple spatial directions. Here, "measurement position" refers to the spatial positioning and orientation of the laser interferometer. When moving the laser interferometer to different measurement positions, a pre-selected fixed distance from the object is maintained. Furthermore, this requires moving the laser interferometer to a new measurement position for each measurement point on the object, which naturally results in a corresponding time consumption for the measurement of the object.

[0009] In DE 10 2007 023 826 A1, the position of a laser interferometer is calibrated using at least one position of a known, freely pre-given point on an object, and a transformation rule is created based on this calibration to determine the position of the laser interferometer relative to the object for any measurement position. Typically, at least three known points on the object are required to determine the position of the laser interferometer in the object's coordinate system, as a total of six degrees of freedom must be determined: three for the laser interferometer's positioning and three for its orientation. For calibration, the corresponding distances between the laser interferometer's position and the corresponding known points, as well as the two angles for measuring the orientation of the laser interferometer's measurement beam, are measured or determined from the beam guiding unit. If four known points exist on the object, the measurement of the distances between each point and the laser interferometer can be omitted.

[0010] In the two existing documents, an industrial robot arm is preferably used as a movable support for the laser interferometer; this provides great flexibility in positioning the laser interferometer and allows the position of the laser interferometer to be predetermined or at least read from the control unit of the industrial robot arm.

[0011] However, the use of industrial robots requires adherence to specific workplace safety measures, such as safety barriers and personnel qualification requirements. Summary of the Invention

[0012] Based on the prior art, the task to be solved by the present invention is to simplify the known non-contact oscillation measurement methods and apparatus, and to accelerate the execution of the measurement.

[0013] This task is solved by the method having the features of claim 1 and by the apparatus having the features of claim 17.

[0014] Preferred improvements to the method according to the invention are given in claims 2 to 17; advantageous design features of the apparatus according to the invention are recorded in claims 18 to 33.

[0015] The method according to the invention includes method steps known per se:

[0016] (a) Position the object on the support.

[0017] (b) Determine multiple measurement points on the object.

[0018] (c) Provide at least one laser interferometer, wherein one or more measurement beams can have their direction changed by means of a corresponding beam guiding unit.

[0019] (d) At least one measurement beam is sequentially directed to the measurement point using a beam guiding unit, and oscillation data is acquired by superimposing the measurement beam reflected or scattered back by the object with the reference beam of the laser interferometer.

[0020] (e) Assign the oscillation data to the measurement points and evaluate the oscillation data.

[0021] (f) Output the evaluated oscillation data associated with the measurement point, preferably in the object-related coordinate system.

[0022] The key point now is that, in method step (a), the object is positioned on a support constructed as a rotating device that can rotate about a rotation axis, and prior to method step (d), a spatial reference (relationship) is established between the laser interferometer, the rotation axis, and the object, and in method step (d), the rotating device is rotated at least once about the rotation axis by a predetermined rotation angle φ or obtained by angle measurement, either by motor drive or manually.

[0023] A spatial reference between the laser interferometer, the axis of rotation, and the object is established through at least two of the following three methodological steps:

[0024] (h1) Establish a spatial reference relationship between the laser interferometer and the rotation axis;

[0025] (h2) Establish a spatial reference relationship between the axis of rotation and the object;

[0026] (h3) Establish a spatial reference relationship between the object and the laser interferometer.

[0027] There is no requirement to position the object on the rotating mechanism; the object can be placed on the turntable, for example, very simply. The important thing is that the object rotates with the rotating mechanism, that is, the object's position relative to the rotating mechanism must not change while the rotating mechanism is rotating.

[0028] Similarly, laser interferometers can be positioned virtually freely in space, for example, using a tripod; they do not need to maintain a specific distance from the object. Likewise, there is no need to move the laser interferometer to another measurement location between measurements.

[0029] A fixed spatial association (correspondence) between the rotating device and the laser interferometer is not necessary. Because by establishing a spatial reference (relationship) between the laser interferometer, the rotation axis, and the object according to the present invention, a common reference system is generated. For example, this reference system can be an object-related coordinate system (but is not required), and in this reference system, the positions of the object, the laser interferometer, and the rotation axis are known.

[0030] The measurement points located on the surface of an object and collectively constituting the basic surface morphology of the object are known in the object's associated coordinate system, for example, by acquiring (capturing) digital images, by photogrammetry, by fringe projection, by a time-of-flight camera, or by reading from an FE model.

[0031] A spatial reference between the laser interferometer and the axis of rotation can be established as follows: At two rotational angular positions of the rotating device, a measurement beam is irradiated onto a point, such as a calibration mark on the rotating device, a point on a separate calibration object rotating with the device, or a measurement point on the object. If the positions of two distinct points of the rotating device, calibration object, or object under test relative to each other are known, it is sufficient to direct the measurement beam to the first point at the first rotational angular position and to the second point at the second rotational angular position. This determines the position of the axis of rotation in the measurement device's reference frame. If not known beforehand, the individual measurement positions of the measuring heads can also be determined relative to each other when using multiple measuring heads. Multiple points and the three rotational angular positions of the rotating device are typically used to improve the accuracy of the position determination.

[0032] As previously described, a laser interferometer, preferably comprising three measuring heads, can be freely positioned in space, with each measuring position of the interferometer being relatively fixed relative to each other during measurement. Here, the multiple measuring heads can be in a known, fixed association relative to each other, or each measuring head can be freely positioned relative to itself. By directing (one) measuring beam, or particularly three measuring beams, to at least three measuring points on the object, a spatial reference between the laser interferometer or its measuring heads and the object can be readily established, as is known per se.

[0033] A spatial reference between the axis of rotation and the object can be established, for example, by using a camera that photographs the object from two different angular positions of rotation, capturing its surface topography. Alternatively, similarly, at the two angular positions of rotation of the rotating device, the positions of at least two points on the object's surface, whose relative positions to each other are known, can be determined, for example, by a measuring beam from a laser interferometer, thereby establishing a reference between the object and the axis of rotation.

[0034] In any case, it is crucial to know the position of the laser interferometer, the position of the rotation axis, and the position of the object under test in a common reference frame, preferably an object-dependent coordinate system. This facilitates the output of the measured and evaluated oscillation data in an object-dependent coordinate system in a particularly easy-to-understand manner.

[0035] The apparatus for non-contact oscillation measurement according to the invention is particularly suitable and configured to perform the method according to the invention. The apparatus includes a support for positioning an object, and at least one laser interferometer with one or more measuring heads, the direction of which can be changed by means of a corresponding beam guiding unit. This is achieved, in particular, by deflecting the measuring beam, preferably within the range of an XY scanner by means of a rotatable lens, wherein the deflection angle and thus the spatial direction of the measuring beam can be predetermined or at least read from the beam guiding unit. Using each measuring beam, oscillation data at the measuring point is acquired by superimposing the measuring beam reflected or scattered back from the measuring point with a reference beam. Simultaneously, the control unit, using a beam guiding unit for each measuring head, sequentially points at least one or more measuring beams onto a plurality of predetermined measuring points on the object. An evaluation unit, cooperating with the control unit, determines the measuring points, assigns the oscillation data from the laser interferometer to the measuring points and evaluates the oscillation data, which is then output by an output unit in association with the measuring points, particularly in an object-related coordinate system.

[0036] In the device according to the invention, the key feature is that the support for positioning the object is a rotating device that can rotate about a rotation axis, particularly constructed as a turntable on which the object can be placed. The control unit is also designed to rotate the rotating device about the rotation axis at least once by a predetermined rotation angle φ via a motor drive, or to record such rotation by angle measurement, which need not be driven by a motor. Afterward, the control unit again simultaneously and successively points at least one or more measuring beams onto multiple predetermined measuring points on the object.

[0037] The evaluation unit is preferably designed to establish a spatial reference between the laser interferometer, the axis of rotation, and the object in order to determine the measurement point and / or correlate the oscillation data with the measurement point, thereby establishing a common reference frame. This is achieved through at least two of the following three measures:

[0038] - Establish a spatial reference relationship between the laser interferometer and the axis of rotation.

[0039] - Establish a spatial reference relationship between the axis of rotation and the object.

[0040] - Establish a spatial reference relationship between the object and the laser interferometer.

[0041] Multiple measurement points are determined on the object, preferably through visualization of the object. Accordingly, the evaluation unit of the device according to the invention is also preferably designed to visualize the object on a display and determine the measurement points through user input in order to determine the measurement points.

[0042] As mentioned earlier, a more suitable beam guiding unit is an XY scanner with controlled, rotatable lenses for targeted deflection of the measurement beam. If multiple measurement heads are used, each measurement beam is equipped with its own beam guiding unit configured in this way.

[0043] Within the framework of the method according to the invention, the object and the laser interferometer are preferably positioned such that, by rotating the rotating device, one or more measurement beams can reach more measurement points than would be achieved if the object were not rotated when one or more measurement beams are successively guided to the measurement points. It has proven advantageous for this to be that the positioning such that at least one measurement beam from the laser interferometer illuminating the object forms an angle α > 20°, preferably α > 45°, and particularly preferably α > 60° relative to the axis of rotation of the rotating device at at least one position of the beam guiding unit.

[0044] The laser interferometer preferably includes at least two, and particularly advantageously three, measuring heads whose measuring beams are at each measuring point with an angle β > 3°, preferably β > 10° between each other, so that oscillating motion in three different spatial directions can be acquired (sensed) at each measuring point.

[0045] To establish a spatial reference between the laser interferometer and the axis of rotation, which may be necessary in the method according to the invention, a calibration mark on the rotating device or a calibration object rotating with the rotating device can be used: its spatial orientation relative to the known measurement beam of the laser interferometer is pointed to the calibration mark or a point with a clear spatial connection to the calibration mark, and then the rotating device is rotated twice to another rotational angular position, guiding the measurement beam to the same point or to a second point, from which the first point can be deduced. The position of the axis of rotation in the reference frame of the laser interferometer can be inferred by the necessary change in the spatial orientation of the laser beam. If the process is performed in such a way as guiding the measurement beam to three different calibration marks, then one rotation of the rotating device is sufficient. Accordingly, a calibration object can also be used, for example, which can be freely positioned on a turntable, and which must also rotate with the rotating device when it rotates to another rotational angular position.

[0046] Alternatively, a camera can be used to capture digital images of the rotating device and / or the calibration object, so that as long as the camera and the laser interferometer are clearly correlated in space, it is not necessary to know the spatial direction of the measurement beam. Because the position of the laser spot on the rotating device or calibration object can be tracked through digital images, the position of the rotation axis can be deduced.

[0047] Accordingly, the apparatus according to the invention preferably has one or more calibration marks on the rotating device, or a calibration object that rotates with the rotating device. It may also include a camera to perform the method already described for establishing a spatial reference between the laser interferometer and the axis of rotation.

[0048] The calibration object can be a freely positionable object on a rotating device, equipped with calibration marks. The calibration marks can also be formed by shaping the calibration object.

[0049] To establish a spatial reference between the axis of rotation and the object, which may be necessary within the scope of the method according to the invention, at least one camera and at least one digital image of the object taken by the camera at at least two different rotational angular positions of the rotating device can be used. The camera can also be used to establish a spatial reference between the object and the axis of rotation; correspondingly, such a camera is preferably present in the device according to the invention.

[0050] Within the scope of this invention, in order to establish a spatial reference between the object and the laser interferometer, the surface morphology of the object can also be determined, including at least the measurement points; for this purpose, the object's structural data, particularly a finite element model (FE model), and / or photogrammetry methods, for which a suitable camera is appropriate, and / or fringe projection and / or time-of-flight cameras can be used. If photogrammetry is used, it is suitable to take camera images at at least two different rotation angle positions of the rotating device, thereby determining the surface morphology.

[0051] For determining a measurement point and assigning it to at least one rotational angular position, it is advantageous that at the corresponding rotational angular position, at least one measurement beam is able to reach the assigned measurement point, and preferably the measurement beam reaches the surface of the object at an incident angle as close as possible to the surface normal, and particularly preferably is not obstructed, for example, by adjacent surface areas, by cables, by oscillating exciters or the like.

[0052] In the apparatus according to the invention, if the evaluation unit is designed to capture images at at least two different rotational angular positions of the rotating device, particularly by photogrammetry, and thereby determine the surface morphology of the object, it is preferable that the evaluation unit is also designed to identify, when determining the surface morphology, measurement points at specific rotational angular positions of the rotating device where one or more measurement beams would be obstructed, for example by adjacent surface areas or objects such as cables.

[0053] The laser interferometer can be mounted on a movable or adjustable measuring stand, or, if desired, on a program-controlled movable measuring stand, so that the position of the laser interferometer can be changed if the measuring point cannot be optimally reached or is not reached at all despite rotating the rotating device. However, the particular advantage of this invention—capable of performing non-contact oscillation measurements with exceptional simplicity and speed—is best realized when the laser interferometer is mounted on a freely positionable tripod, which does not preclude moving the tripod or changing its height to ensure optimal reach of the measurement beam to the measuring point.

[0054] Finally, within the scope of this invention, it is preferable to position the oscillation exciter on the rotating device in order to excite the oscillation of the object for oscillation measurement.

[0055] Therefore, the method and apparatus according to the invention enable particularly simple and rapid non-contact measurement of object oscillations, requiring only the object to be placed on a turntable or other rotating device. The software can then automatically handle: determining the measurement point (optionally, this can also be done by the user on a display), establishing a common reference frame between the laser interferometer, the object, and the axis of rotation, determining the optimal rotation angle for measurement at the measurement point, and then sequentially performing the oscillation measurement while gradually rotating the rotating device. Measurements can continue immediately after the rotating device has rotated, provided the laser interferometer and object have not been adjusted, significantly accelerating the entire measurement process compared to existing technologies.

[0056] The evaluation of the oscillation data thus acquired can then be output specifically based on the visualization (display) of the object under test. Advantageously, apart from the lenses in one or more XY scanners and the rotation mechanism, no mechanical movement of the components of the device according to the invention is required. Attached Figure Description

[0057] The following description, based on the accompanying illustrative drawings, will depict embodiments of the apparatus for non-contact oscillation measurement constructed according to the invention, thereby deriving embodiments of the method according to the invention. The drawings show:

[0058] Figure 1 This is an example of the structure of a device constructed according to the present invention;

[0059] Figure 2 During the measurement process Figure 1 The structure;

[0060] Figure 3 In another stage of the measurement process Figure 1 The structure;

[0061] Figure 4 Show Figure 1 The structure includes an adjustable measuring bracket for use with a laser interferometer;

[0062] Figure 5 It is similar to Figure 4 The diagram is used to illustrate angular relationships;

[0063] Figure 6 This diagram illustrates the angular relationship between the beam guiding unit and the measuring beams, showing three measuring beams incident on a single measuring point.

[0064] Figure 7 When preparing for another measurement process Figure 1 The structure;

[0065] Figure 8 When preparing for another measurement process Figure 1 The structure;

[0066] Figure 9 shows an example structure of another device constructed according to the present invention during the measurement process;

[0067] Figure 10 When establishing a common reference frame between the object, the axis of rotation, and the laser interferometer Figure 1 The structure;

[0068] Figure 11 It is similar to Figure 10 The illustration, but at a later moment:

[0069] Figure 12 It is a structure used to establish a common reference system;

[0070] Figure 13 It is a structure used to establish a common reference system. Detailed Implementation

[0071] exist Figure 1The diagram schematically illustrates the structure of an example of a device constructed according to the invention. The components of the device shown are: an object 1 whose oscillation characteristics are to be measured; a laser interferometer 2, in this embodiment consisting of three separate measuring heads 2.1, 2.2, and 2.3, which are fixedly mounted relative to each other by means of a measuring bracket 3, but can also be freely positioned, as their respective measuring positions can be determined within the scope of the method according to the invention; a rotating device 4 configured as a turntable 10 serving as a bracket 5 on which the object 1 is positioned, wherein the rotating device 4 in this embodiment can be rotated about a rotation axis 7 by means of a drive motor 6. An encoder 8 at the rotating device 4 is used to determine the rotation angle φ about the rotation axis 7.

[0072] Figure 1 The structure shown also includes a camera 9, which in this embodiment is fixedly mounted in the laser interferometer 2 and correspondingly and explicitly assigned to (associated with) the laser interferometer 2. It should be noted that the camera 9 can also be freely positioned in space, and multiple cameras can be used to improve the accuracy of the standard (adjustment) and measurement.

[0073] The rotating device 4, or more precisely, the turntable 10, has a calibration mark 11 for establishing a spatial reference between the laser interferometer 2 and the rotation axis 7 or between the rotation axis 7 and the object 1, which will be discussed below.

[0074] Control unit 12 controls drive motor 6 and laser interferometer 2, more precisely, its beam guiding unit, which is not visible in the current illustration, but for each measuring head 2.1, 2.2, 2.3, consists of a conventional XY scanner with rotatable lenses for deflecting the laser beam emitted from the measuring head. Control unit 12 is implemented as software in a commercial computer.

[0075] like Figure 1 As shown, each measuring head 2.1, 2.2, and 2.3 of the laser interferometer 2 emits a measuring beam 13, which is directed at one of a plurality of measuring points 14 on the object 1. Figure 1 In the diagram, three measuring beams 13 are shown for each measuring head 2.1, 2.2, and 2.3, respectively, to symbolize that the measuring beams 13 scan the measuring points 14 on the object 1, thereby measuring all the measuring points 14 on the object 1 in sequence. For this purpose, an oscillation exciter 15 is arranged on the turntable 10 to excite the object 1 to oscillate.

[0076] Figure 2 and Figure 3 With the help of similar Figure 1The diagram illustrates the measurement process: In the first angular position φ1 of the rotating device 4, the object 1 is excited to oscillate by means of the oscillation exciter 15, and the laser interferometer 2 scans the measurement point 14 of the object 1 that can be optimally reached in this rotational angular position φ1, and collects the corresponding oscillation data for each measurement point 14.

[0077] like Figure 3 As shown, after object 1 rotates around rotation axis 7 using rotating device 4, measurement continues, and object 1 is now at the second rotation angle position φ2. Now, the laser interferometer 2 measures the measurement point 14 that can be optimally reached at this rotation angle position φ2, while the oscillation exciter 15 continues to excite object 1 to oscillate.

[0078] In the same commercial computer where the control unit 12 is implemented as software, the evaluation unit 16 is also implemented as software, which collaborates with the control unit 12 to determine the measurement point 14, assign oscillation data from the laser interferometer 2 to the measurement point 14, and evaluate the oscillation data. Also in the same computer, the output unit 17 is implemented, for example, as shown, to visualize the object 1 on the display 18 and output its measured oscillation characteristics in the object-related coordinate system 19.

[0079] Figure 4 It is shown again Figures 1 to 3 The illustrations of the embodiment illustrate that the laser interferometer 2 can be freely positioned in space relative to the rotating device 4: Figure 4 In the upper part of the diagram, the laser interferometer 2 is mounted on the measuring bracket 3 as shown in the previous diagrams; unlike the others, Figure 4 The lower part of the figure illustrates that the laser interferometer 2 is mounted at a higher position on the measuring bracket 3, that is, it is offset on the measuring bracket 3, so as to better measure the upward surface of the object 1: the measuring beam 13 then illuminates this upper surface of the object 1 at a smaller acute angle than it might have pointed when the interferometer 2 was not adjusted.

[0080] Figure 5 Corresponding to Figure 4 The illustration in the lower part of the figure illustrates the angle α of the measuring beam 13 relative to the rotation axis 7 at a specific measuring point 14. This angle should be greater than 20 degrees for the multiple measuring points 14 and all three measuring heads 2.1, 2.2 and 2.3, preferably greater than 45 degrees, and particularly preferably greater than 60 degrees.

[0081] Figure 6To clarify, the three measuring beams 13 of the three measuring heads 2.1, 2.2, and 2.3 of the laser interferometer 2 form angles β1, β2, and β3 relative to each other at each measuring point 14. These angles are greater than 3 degrees and preferably greater than 10 degrees, so that the oscillation characteristics of the object 1 in three different spatial directions can be acquired and evaluated at the measuring point 14. For the first measuring beam 13, two lenses 20 and 21 act as XY scanners, serving as beam guiding units 22. These lenses deflect the measuring beam 13 in the first spatial direction through a first deflection angle ψ1 and a second deflection angle ψ2 perpendicular to it, so that it can reach all measuring points 14 sequentially. The other two measuring beams 13 are deflected in the same way by means of the same lenses 20 and 21, so that the measuring beams 13 intersect at their respective measuring points 14.

[0082] Figure 7 and Figure 8 The preparation for the measurement is shown, as in... Figure 2 and Figure 3 As shown in another object 1. Figure 7 and Figure 8 The object 1 shown is more irregularly shaped, so it is meaningful to assign rotational angular positions φ1 and φ2 to each measurement point 14, in which the measurement beam 13 illuminates the surface of the object 1 as close as possible to the surface normal when it is pointed at the corresponding measurement point 14. For this purpose, an evaluation unit 16 is used, in which an image of the object 1 is displayed by means of a camera 9. Through user input, those measurement points 14 that are optimally reachable at rotational angular positions φ1 can be identified.

[0083] exist Figure 8 In the evaluation unit, the measurement points 14 selected by the user input are the best measurable in the changed rotation angle position φ2.

[0084] Figure 9a , Figure 9b and Figure 9c An embodiment of the device constructed according to the present invention is shown, wherein the laser interferometer 2 includes only one measuring head. A single measuring beam 13 is directed at the measuring point 14, while the oscillator 15 excites the object 1 to oscillate.

[0085] exist Figure 9a This occurs at the first rotation angle position φ1. Afterwards, the rotating device 4 rotates about the rotation axis 7, such that... Figure 9b As shown, measurements can be taken at the same measurement point 14 within the second rotation angle position φ2. Figure 9c Finally, as shown, the same measurement point 14 is measured again at the third rotation angle position φ3, so that the result of this measurement point 14 is the same as that of the laser interferometer 2 with three measuring heads, providing oscillation data in three different spatial directions.

[0086] Figure 10 and Figure 11 This paper clarifies how a common reference frame can be established for the rotation axis 7, the object 1, and the laser interferometer 2 according to the present invention, even though the object 1 is freely positioned on the turntable 10 and the laser interferometer 2 can also be freely positioned in space.

[0087] In this example, object 1 is a calibration object 23 with multiple markings 24 printed on it, the positions of which are known. By pointing the measuring beam 13 at as many of the markings 24 as possible on the calibration object 23, the positions (localization and orientation) of the measuring heads 2.1, 2.2, and 2.3 can be determined, thereby determining the position of the laser interferometer 2 in the object-related coordinate system 19.

[0088] Now, as Figure 11 As shown, if the rotating device 4 is rotated by a specific rotation angle φ, for example, 20 degrees, the position of the rotation axis 7 in the object-related coordinate system, which in this case is the position in the coordinate system 25 of the calibration object 23, can be determined by re-acquiring the mark 24 on the calibration object 23. This naturally applies not only to the object-related coordinate system but also to the measuring device reference system or the rotation axis-related coordinate system. The important thing is to find a common reference system in order to perform and evaluate the oscillation measurements according to the invention. Referring to the object-related coordinate system is advantageous here because the evaluated oscillation data can then be visualized and output particularly easily.

[0089] An example of a method constructed according to the present invention and performed on the apparatus shown in the accompanying drawings is as follows:

[0090] The laser interferometer 2, constructed as a 3D scanning vibrometer, consists of three measuring heads 2.1, 2.2, and 2.3. Each measuring head carries an XY scanner (serving as a beam guiding unit 22) and a laser vibrometer, and is positioned on a fixed (non-programmably movable) measuring bracket 3 (each measuring head can be freely positioned relative to the rotating device 4). In the first step, a calibration object 23 is positioned on the rotating device 4. The calibration object 23 is an object with known coordinates, onto which the laser beam can be easily and safely positioned. The positions (positioning and orientation) of the measuring heads 2.1, 2.2, and 2.3 are determined using the calibration object 23 by aligning the laser beam to at least three, preferably more, points on the calibration object 23 using the XY scanner. The positions of the measuring heads 2.1, 2.2, and 2.3 can be calculated based on the deflection angle ψ and the coordinates x, y, and z of the points on the calibration object 23. The positions are determined in the coordinate system of the calibration object 23.

[0091] After the rotation axis 7 is rotated to another rotation angle φ2, the process of determining the positions of measuring heads 2.1, 2.2, and 2.3 in the coordinate system 25 of the calibration object 23 is repeated. It is advantageous to know the angular difference between the two rotation angle positions φ1 and φ2, which can typically be provided beforehand or at least read from the control unit 12 of the rotating device 4. Starting from these two positions of measuring heads 2.1, 2.2, and 2.3 in the coordinate system 25 of the calibration object 23, the position of the rotation axis 7 relative to the calibration object 23 can be determined in a further step. Advantageously, in the coordinate system 25 of the calibration object 23, at least one further calibration is performed at at least one additional rotation position φ3 for the positions of measuring heads 2.1, 2.2, and 2.3. Result: At a known rotation angle φ... x In this case, the positions of measuring heads 2.1, 2.2, and 2.3 in the coordinate system of rotation axis 7 can now be calculated at any time based on existing information. In summary, the mathematical model of the rotating device 4 is calculated. After this process step, the calibration object 23 is removed from the rotating device 4.

[0092] The object 1, whose oscillations are to be measured, and the actuator or oscillation exciter 15 for generating the oscillations are positioned on the rotating device 4. For the object 1, there exists a geometry file containing the coordinates of the measurement point 14 where the oscillation characteristics are to be measured. The geometry file can be generated, for example, through a data interface to construction data, particularly FE models, or by scanning with the aid of a 3D scanner, or by the aid of a camera 9.

[0093] In the next step, the position of the object under test 1 relative to the rotation axis 7 is determined. This can be achieved, for example, by covering at least three points with known coordinates of the object under test 1 with the measuring beams 13 of the three measuring heads 2.1, 2.2, and 2.3. The corresponding coordinates in the 3D geometry must be known, i.e., the point must be identifiable. With this information, the positions of the measuring heads 2.1, 2.2, and 2.3 in the coordinate system of the object under test 1 can be calculated for each rotation angle φ of the turntable 10.

[0094] To reach all predefined points on object 1 using the measuring beam 13, multiple rotational angular positions of the turntable 10 are required. Based on the geometric file and the positions of the measuring heads 2.1, 2.2, and 2.3 in the coordinate system of object 1, it can be determined which points of object 1 can be located at which rotational position φ of the turntable 10. xThe position of the measuring heads 2.1, 2.2, and 2.3, reached using an XY scanner, varies depending on the set rotation angle φ of the turntable 10. These calculations allow for the automation of the measurement process at the measurement point 14 of the object 1 by driving at least two rotational positions φ1 and φ2 toward the turntable 10, and measuring different measurement points 14 of the object 1 at each rotational position φ1 and φ2. Here, the rotational positions φ1 and φ2 can be either pre-given by the user or calculated during optimization to minimize the number of rotational positions φ1 and φ2. x Reach as many measurement points as possible 14.

[0095] If the measurement point 14 of object 1 can be located at multiple rotation angle positions φ of turntable 10 x It is advantageous to arrive at the position where the angle of incidence of the measuring beam 14 onto the object 1 is a favorable rotation angle. A favorable angle of incidence is the angle at which as much light as possible is reflected, i.e., an angle with small deviation from perpendicular incidence. It is also advantageous that the laser interferometer 2 can be arbitrarily positioned in height and tilt relative to the axis of rotation 7, thereby also being able to measure objects 1 with complex geometries and different sizes.

[0096] After completing the oscillation measurements at all 14 measurement points, the results can be summarized. This requires calculating the φ values ​​at each rotation angle of the turntable 10. x The measurement results are transformed into a common coordinate system (suitably the coordinate system of the object to be measured 1).

[0097] However, within the scope of this invention, establishing a common reference frame can also be done without the use of calibration object 23, particularly when using camera 9. The camera 9 shown in the figures is fixedly connected to the laser interferometer 2; however, within the scope of this invention, this is not absolutely necessary, as camera 9 can also be freely positioned in space, such as... Figure 12 and Figure 13 As shown.

[0098] The following describes two exemplary methods, constructed according to the present invention, for establishing a common reference frame or spatial reference as described in method features h1, h2, and h3:

[0099] 1. Using photogrammetry:

[0100] 1.1 Method and Procedure (h1): Establish a spatial reference between the rotation axis 7 of the laser interferometer 2 and the rotating device 4:

[0101] Only steps (h2) and (h3) are performed. The reference between the laser interferometer 2 and the rotation axis 7 can be established in two steps: first, the laser interferometer 2 is associated with the object 1, and then the object 1 is associated with the rotation axis 7. This allows, for example, the determination of the position of the laser interferometer 2 relative to the object 1 in each turntable position.

[0102] 1.2 Method and Steps (h2): Establish a spatial reference between the rotation axis 7 and object 1:

[0103] At least one camera 9 is freely positioned relative to the object 1 and the turntable 10, having a viewing angle toward the object 1. Multiple cameras are advantageous for improving accuracy, reducing occlusion in photogrammetry, and determining the surface topography of the object 1 without moving the turntable 10.

[0104] Camera 9 at multiple rotation angle positions φ on turntable 10 x Digital images are captured at the location. These images are analyzed using a photogrammetric method (e.g., as described in https: / / www.mdpi.com / 2079-9292 / 8 / 12 / 1441). The surface morphology of object 1, the support, the oscillation exciter 15, the cable, etc., is thus obtained. The position of camera 9 relative to object 1 or turntable 10 in the coordinate system of the surface morphology is then determined for each rotation angle φ of turntable 10.

[0105] In the coordinate system related to the object, due to the rotational motion of the turntable 10 and the fixed camera 9, the position of the camera 9 lies on a circle, such as... Figure 13 As shown.

[0106] By fitting a circle, the perpendicular line to the center of the circle can be determined, thereby determining the axis of rotation 7 in the coordinate system of the surface morphology.

[0107] 1.3 Method and Procedure (h3): Establish a spatial reference between object 1 and laser interferometer 2:

[0108] The turntable 10 is driven to the following rotational angular position φ, at which a digital image for determining the surface topography has been previously captured, and the position of the camera 9 relative to the surface topography or object 1 is thus known.

[0109] The measurement beam 13 is directed onto the object 1 using the beam guiding unit 22 of the laser interferometer 2. A digital image is captured using the camera 9. Here, the shutter speed of the camera 9 is advantageously selected, and the aperture is selected if necessary, so that only the incident point of the measurement beam 13 on the object 1 (the laser spot) is clearly visible, while all other image content is underexposed. The position of the laser spot is determined, for example, by determining the centroid of the exposed pixels of the digital image, taking into account the brightness of the pixels.

[0110] Through photogrammetry (and calibrations known to camera 9 or performed during photogrammetry), the direction of a line of sight relative to the surface topography, originating from camera 9 and passing through the centroid of the laser spot in the captured image, is known. For this line of sight, its intersection with the surface topography in the coordinate system of the surface topography or the coordinate system of object 1 is determined.

[0111] By using the deflection angles ψ1 and ψ2 of the beam guiding unit 22, the beam path of the measurement beam 13 relative to the laser interferometer 2 is known. Furthermore, the position of a point on the beam path of the measurement beam 13 in the coordinate system of the surface topography or the coordinate system of the object 1 is thus known. This process is performed for at least three, and advantageously significantly more, additional directions of the beam guiding unit 22 of the laser interferometer 2.

[0112] From this information, the position of the laser interferometer 2 relative to the surface topography or relative to the object 1 is determined through fitting. To improve accuracy and robustness, it is advantageous to use multiple rotational angular positions φ of the turntable 10. x Repeat the process at the location and average the corresponding determined position of the laser interferometer 2.

[0113] 2. Using the method of calibrating object 23:

[0114] 2.1. Method and Steps (h1): Establish a spatial reference between the laser interferometer 2 and the rotation axis 7 of the rotating device 4:

[0115] A calibration object 23 marked 24 (whose position is known in the coordinate system 25 of the calibration object 23) is positioned on the turntable 10 such that it moves with the rotation of the turntable 10 without (relatively) moving, and can be illuminated at multiple points by the measurement beam 13 of the laser interferometer 2 at the current rotational angular position φ of the turntable 10. Advantageously, the orientation is approximately perpendicular to the principal direction of the measurement beam 13 of the laser interferometer 2.

[0116] Camera 9 is freely positioned relative to calibration object 23 and turntable 10, having a viewing angle toward calibration object 23. Camera 9 can be mounted in laser interferometer 2. Digital images are captured using camera 9. The position of marker 24 is determined in the images, and a model of camera 9 is built, allowing each pixel of the image from camera 9 to be associated with a coordinate in the coordinate system of calibration object 23.

[0117] The measurement beam 13 of the laser interferometer 2 is directed onto the calibration object 23. The beam direction of the measurement beam 13 relative to the laser interferometer 2 is known through the deflection angles ψ1 and ψ2 of the beam guiding unit 22.

[0118] A digital image is captured using camera 9. Here, the shutter speed of camera 9 is advantageously selected, and the aperture is selected if necessary, so that only the point of illumination (laser spot) of the measurement beam 13 on object 1 is clearly visible, while all other pixels are dark. The position of the laser spot is determined, for example, by determining the centroid of the exposed pixel considering the pixel's brightness; alternatively, the exposed pixel can also be determined by user input, for example, in a video image. Thus, the coordinates of the laser spot in the coordinate system 25 of the calibration object 23 are known. This process is performed for at least three additional directions of the beam guiding unit 22 of the laser interferometer 2.

[0119] From this information, a first position of the laser interferometer 2 relative to the calibration object 23 is determined by fitting. This process is repeated at at least one additional rotational angular position φ of the turntable 10, thereby determining a second position of the laser interferometer 2 relative to the calibration object 23.

[0120] Determine the coordinate transformation from the first position to the second position, such as rotation and translation. From this transformation, determine the position of the rotation axis 7 in the coordinate system of the calibrated object 23.

[0121] The position of the interferometer 2 is also known in the coordinate system 25 of the calibration object 23, thus establishing a reference between the position of the laser interferometer 2 and the rotation axis 7.

[0122] To improve accuracy and robustness, it is advantageous to have multiple rotational angular positions φ of the turntable 10. x Repeat the process at the point and average the position of the corresponding determined rotation axis 7.

[0123] 2.2. Method and Steps (h2): Establish a spatial reference between the rotation axis 7 and object 1:

[0124] Only steps (h1) and (h3) are performed. The reference between the rotation axis 7 and the object 1 can be established in two steps. First, associate the laser interferometer 2 with the rotation axis 7, and then associate the object 1 with the laser interferometer 2.

[0125] 2.3. Method and Procedure (h3): Establish a spatial reference between object 1 and laser interferometer 2:

[0126] The measurement beam 13 of the laser interferometer 2 is directed to a prominent point on the surface of the object 1, for example, through user input. The beam direction of the measurement beam 13 relative to the laser interferometer 2 is known by the deflection angles ψ1 and ψ2 of the beam guiding unit 22.

[0127] The laser spot on the surface of object 1 is assigned to a corresponding point on the surface topography of the object (known, for example, through CAD or FE models, photogrammetry, or 3D scanning). Thus, the coordinates of the point of illumination (incident point) of the measurement beam 13 on the surface of object 1 relative to object 1 are known. This process is performed for at least three other directions of the beam guiding unit 22 of the laser interferometer 2.

[0128] The position of laser interferometer 2 relative to object 1 is determined by fitting this information.

[0129] 3. Common steps for methods 1 and 2 above:

[0130] - Select measurement point 14 from the surface morphology of object 1.

[0131] - Assign the measuring point 14 to the appropriate rotation angle position φ of the turntable 10. x Here, for a given rotation angle position φ x The beam trajectory of the measurement beam 13 of the laser interferometer 2 relative to the object 1 is calculated. Therefore, the position of the laser interferometer 2 relative to the object 1 is calculated. Here, the position of the laser interferometer 2 relative to the rotation axis 7 relative to the object 1 is used to calculate the rotation angle φ. x The transformation. Determine the angle of incidence relative to the surface normal of object 1. Determine whether the beam path is blocked by other parts of the surface topography of object 1. Advantageously, if the information (terrain) used by the software for calculation is incomplete or too coarse, the user can check and change the assignment (association).

[0132] - Advantageously, the measuring point 14 is assigned to multiple rotational angular positions φ of the turntable 10. x .

[0133] -At least those rotational angular positions φ of the associated measurement points 14 facing the turntable 10. x drive.

[0134] -The measurement beam 13 is directed by the beam guiding unit 22 to the rotation angle position φ assigned (associated with) that rotation angle position. x The measurement point is 14. It is advantageous to check the positioning in the camera image. This can be done automatically by determining the position of the laser beam in the video image as described above. In the case of multiple laser interferometers, this is done sequentially. Measurement is only performed when all laser beams have reached the target; otherwise, the measurement point is repeated at another rotation angle position.

[0135] - Oscillation data is acquired by laser interferometer 2 and assigned to the corresponding measurement point 14.

[0136] -If a different rotation angle φ already exists for this measurement point 14.y The oscillation data measured at point 14 can be used to evaluate the signal quality of the measurement and assign the best measurement to the measurement point 14.

[0137] List of reference numerals in the attached diagram:

[0138] 1. Object

[0139] 2. Laser Interferometer

[0140] 2.1 Measuring head

[0141] 2.2 Measuring head

[0142] 2.3 Measuring head

[0143] 3. Measuring bracket

[0144] 4. Rotating device

[0145] 5 supports

[0146] 6 drive motors

[0147] 7. Axis of rotation

[0148] 8 encoders

[0149] 9 cameras

[0150] 10 turntables

[0151] 11 Calibration Marks

[0152] 12 Control Units

[0153] 13 Measuring the beam

[0154] 14 Measurement Points

[0155] 15 Oscillation Exciter

[0156] 16 Evaluation Units

[0157] 17 Output Unit

[0158] 18 monitors

[0159] 19. Coordinate system related to the object

[0160] 20 Lenses ψ1

[0161] 21 Lens ψ2

[0162] 22 Beam Guiding Units

[0163] 23. Calibrate the object

[0164] 24 Mark (on calibration object 23) 25 Coordinate system of calibration object φ Rotation angle ψ Deflection angle α Measurement beam / rotation axis angle β Measurement beam / measurement beam angle.

Claims

1. A method for non-contact measurement of object oscillation, comprising the following steps: (a) Position the object on the support. (b) Determine multiple measurement points on the object. (c) Provide at least one laser interferometer, wherein one or more measurement beams can change their direction by means of a corresponding beam guiding unit. (d) Using the beam guiding unit, at least one measurement beam is sequentially directed to the measurement point, and oscillation data is sensed by superimposing the measurement beam reflected or scattered back by the object with the reference beam of the laser interferometer. (e) Assign the oscillation data to the measurement point and evaluate the oscillation data. (f) Output the evaluated oscillation data, which is associated with the measurement point, preferably in an object-related coordinate system. Its features are, (g) In method step (a), the object is positioned on a support configured as a rotating device, the support being rotatable about a rotation axis. (h) Prior to method step (d), a spatial reference is established between the laser interferometer, the axis of rotation, and the object by at least two of the following three method steps: (h1) Establish a spatial reference between the laser interferometer and the rotation axis of the rotating device. (h2) Establish a spatial reference between the axis of rotation and the object. (h3) Establish a spatial reference between the object and the laser interferometer. (i) In method step (d), the rotating device rotates at least once around the rotation axis by a predetermined rotation angle φ or sensed by angle measurement.

2. The method according to claim 1, Its features are, In method step (b), determining the plurality of measurement points on the object is performed on a display by visualizing the object.

3. The method according to claim 1 or 2, Its features are, At least one beam guiding unit uses a controlled, rotatable lens to selectively deflect at least one measuring beam.

4. The method according to at least one of claims 1 to 3, Its features are, A turntable is used as a rotating device.

5. The method according to at least one of claims 1 to 4, Its features are, In method steps (a) and (c), the object and the laser interferometer are positioned such that by rotating the rotating device, one or more measurement beams can reach more measurement points than in method step (d) where the object is not rotated.

6. The method according to at least one of claims 1 to 5, Its features are, At least one measuring beam of the laser interferometer, illuminating the object, forms an angle α with respect to the rotation axis of the rotating device at at least one position of the beam guiding unit, wherein α > 20°, preferably α > 45° and particularly preferably α > 60°.

7. The method according to at least one of claims 1 to 6, Its features are, A laser interferometer with at least two, preferably three, measuring heads is used, wherein the measuring beams of the laser interferometer are at each measuring point at an angle β > 3°, preferably β > 10°.

8. The method according to at least one of claims 1 to 7, Its features are, In order to establish a spatial reference between the laser interferometer and the rotation axis, prior to method step (d), at least one calibration mark on the rotating device or a calibration object rotating with the rotating device is used at at least two rotation angle positions φ1, φ2 of the rotating device.

9. The method according to claim 8, Its features are, To establish a spatial reference between the laser interferometer and the rotation axis, at least one camera and at least one digital image of the rotating device or the calibration object captured by the camera are used.

10. The method according to at least one of claims 1 to 9, Its features are, In order to establish a spatial reference between the axis of rotation and the object, prior to method step (d), at least one digital image of the object is taken by at least one camera and at least two different rotation angle positions φ1 and φ2 of the rotating device.

11. The method according to at least one of claims 1 to 10, Its features are, In order to establish a spatial reference between the object and the laser interferometer, prior to method step (d), at least one of the cameras and at least one digital image of the object taken by the cameras are used.

12. The method according to at least one of claims 1 to 11, Its features are, In order to establish a spatial reference between the object and the laser interferometer, prior to method step (d), the surface topography of the object is determined, including at least the measurement points; and for this purpose, the object's structural data and / or photogrammetry methods are used.

13. The method according to claim 12, Its features are, The surface morphology is determined by photogrammetry at at least two different rotation angle positions φ1 and φ2 of the rotating device.

14. The method according to any one of claims 10 to 13, Its features are, During or after determining the surface morphology, or based on captured digital images, identify measurement points at specific rotational angular positions of the rotating device that would be obstructed for one or more measurement beams.

15. The method according to at least one of claims 1 to 14, Its features are, In method step (b), the measurement point is assigned accordingly to at least one rotational angular position φ. x At the rotation angle position φ x In this process, at least one of the measuring beams is able to reach the measuring point, and preferably the measuring beams reach the surface of the object at an angle of incidence as close as possible to the surface normal, and particularly preferably without obstruction.

16. The method according to at least one of claims 1 to 15, Its features are, An oscillation exciter is positioned on the rotating device to excite the object to oscillate.

17. An apparatus for non-contact measurement of object oscillations, particularly for performing the method according to at least one of claims 1 to 16, comprising: - A support for positioning the object. - At least one laser interferometer, wherein one or more of the measurement beams of the laser interferometer can change their direction by means of their respective beam guiding units, and accordingly acquires oscillation data at the measurement point by superimposing the measurement beams reflected or scattered back from the measurement point on the object with a reference beam. - A control unit for sequentially guiding at least one of the measuring beams to a plurality of predetermined measuring points on the object using a beam guiding unit. An evaluation unit is configured to determine the measurement point, assign the oscillation data from the laser interferometer to the measurement point, and evaluate the oscillation data, wherein the evaluation unit is designed to cooperate with the control unit. - Output unit, used to output the evaluated oscillation data in association with the measurement points, preferably in an object-related coordinate system. Its features are, - The support is a rotating device that can rotate around its axis of rotation. Furthermore, the control unit is also designed to rotate the rotating device around the rotation axis at least once by a predetermined rotation angle φ via a motor drive, or to sense such rotation by angle measurement, after which the control unit again sequentially guides at least one of the measurement beams onto a plurality of predetermined measurement points on the object.

18. The apparatus according to claim 17, Its features are, The evaluation unit is designed to establish a spatial reference between the laser interferometer, the axis of rotation, and the object by at least two of the following three measures in order to determine the measurement point and / or assign oscillation data to the measurement point: - Establish a spatial reference between the laser interferometer and the rotation axis. - Establish a spatial reference between the axis of rotation and the object. - Establish a spatial reference between the object and the laser interferometer.

19. The apparatus according to any one of claims 17 or 18, Its features are, The evaluation unit is designed to visualize the object on a display and determine the measurement point through user input in order to identify the measurement point.

20. The apparatus according to at least one of claims 17 to 19, Its features are, The beam guiding unit includes a controllable rotating lens for targeted deflection of the measurement beam.

21. The apparatus according to at least one of claims 17 to 20, Its features are, The rotating device is a turntable.

22. The apparatus according to at least one of claims 17 to 21, Its features are, The laser interferometer is arranged relative to the object such that at least one of the measuring beams of the laser interferometer irradiating the object forms an angle α > 20°, preferably α > 45°, and particularly preferably α > 60° relative to the axis of rotation of the rotating device at at least one position of the beam guiding unit.

23. The apparatus according to at least one of claims 17 to 22, Its features are, The laser interferometer includes at least two, preferably three, measuring heads, whose measuring beams are at each measuring point with an angle β>3°, preferably β>10° between them.

24. The apparatus according to at least one of claims 17 to 23, Its features are, In order to establish a spatial reference between the laser interferometer and the rotation axis, the rotating device has at least one calibration mark and / or is provided with a calibration object that rotates together with the rotating device.

25. The method according to claim 24, Its features are, At least one camera is provided for taking at least one digital image of the rotating device or the calibration object at at least two rotation angle positions φ1 and φ2 of the rotating device.

26. The apparatus according to any one of claims 24 or 25, Its features are, The calibration object is an object that can be freely positioned on the rotating device, and preferably has calibration marks.

27. The apparatus according to at least one of claims 17 to 26, Its features are, In order to establish a spatial reference between the laser interferometer and the object and / or between the object and the axis of rotation, at least one camera is provided to capture digital images of the object at at least two rotational angular positions φ1 and φ2 of the rotating device.

28. The apparatus according to at least one of claims 17 to 27, Its features are, The evaluation unit is designed to determine the surface morphology of the object, including at least the measurement points, and uses the object's structural data and / or photogrammetry methods for this purpose.

29. The method according to claim 28, Its features are, The evaluation unit is designed to determine the surface morphology by using photogrammetry at at least two different rotation angle positions φ1 and φ2 of the rotating device.

30. The apparatus according to any one of claims 28 or 29, Its features are, The evaluation unit is designed to identify, when determining the surface morphology, the measurement points at a specific rotation angle position of the rotating device where one or more measurement beams would be obstructed.

31. The apparatus according to at least one of claims 17 to 30, Its features are, The evaluation unit is designed to assign the measurement points to at least one rotation angle position φ. x At the rotation angle position φ x In this process, one or more of the measuring beams are able to reach the measuring point, and preferably one or more of the measuring beams reach the surface of the object at an angle of incidence as close as possible to the surface normal, and particularly preferably without being obstructed.

32. The apparatus according to at least one of claims 17 to 31, Its features are, The laser interferometer is mounted on a tripod that can be freely positioned.

33. The apparatus according to at least one of claims 17 to 32, Its features are, An oscillation exciter is positioned on the rotating device to excite the object to oscillate.

Images